001/* 002 * Copyright (C) 2011 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 005 * in compliance with the License. You may obtain a copy of the License at 006 * 007 * http://www.apache.org/licenses/LICENSE-2.0 008 * 009 * Unless required by applicable law or agreed to in writing, software distributed under the License 010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 011 * or implied. See the License for the specific language governing permissions and limitations under 012 * the License. 013 */ 014 015package com.google.common.util.concurrent; 016 017import com.google.common.annotations.GwtCompatible; 018import java.util.concurrent.Future; 019import org.checkerframework.checker.nullness.qual.Nullable; 020 021/** 022 * Transforms a value, possibly asynchronously. For an example usage and more information, see 023 * {@link Futures#transformAsync(ListenableFuture, AsyncFunction, Executor)}. 024 * 025 * @author Chris Povirk 026 * @since 11.0 027 */ 028@GwtCompatible 029@FunctionalInterface 030@ElementTypesAreNonnullByDefault 031public interface AsyncFunction<I extends @Nullable Object, O extends @Nullable Object> { 032 /** 033 * Returns an output {@code Future} to use in place of the given {@code input}. The output {@code 034 * Future} need not be {@linkplain Future#isDone done}, making {@code AsyncFunction} suitable for 035 * asynchronous derivations. 036 * 037 * <p>Throwing an exception from this method is equivalent to returning a failing {@code Future}. 038 */ 039 ListenableFuture<O> apply(@ParametricNullness I input) throws Exception; 040}